Plastic crate structure with lattice-work bottom



y 1969 1.. M. R. WETTLEN ET AL 3,443,717

PLASTIC CRATE STRUCTURE WITH LATTICE-WORK BOTTOM Filed May a, 1967 Sheet of 2 May 13, 1969 1.. M. R. WETTLEN ET AL 3,443,717

PLASTIC CRATE STRUCTURE WITH LATTICE-WORK BOTTOM Filed May a, 1967 Sheet 3 of 2 3,443,717 PLASTIC CRATE STRUCTURE WITH LATTICE- WORK BOTTOM Lars Malte Roland Wettlen, Lomma, and Curt Ingvar Christopherson, Hassleholm, Sweden, assignors to AB Tetra Pak, Lund, Sweden, a Swedish company Filed May 8, 1967, Ser. No. 636,961 Claims priority, application Sweden, May 9, 1966, 6,340/ 66 Int. Cl. B65d 7/42; E04c 2/42; E04f 19/10 U.S. Cl. 220-66 3 Claims ABSTRACT OF THE DISCLOSURE A crate structure includes a bottom moulded from plastic material and which is constituted by a lattice made up from a criss-cross network of diagonally extending bars which intersect one another at their mutual crossing points. Stress relieving rings are incorporated into some of the intersections between the bars to prevent deformation of the cratebottom in the event that initial stresses are developed in the bottom as a result of the moulding operation. The rings are arranged in mutually perpendicular rows along the bottom and are located at every other intersection along each of the diagonally extending bars.

The present invention refers to a lattice-work made from a plastic material by compression or injection moulding. More closely the invention relates to a crate, the bottom of which is made of such lattice-work.

One has long manufactured plastic crates, the bottoms of which for several reasons have been provided with apertures or other recesses. According to the present construction the bottom is intended to consist of a latticework, whereby a considerable saving of material is achieved at the same time the crate will be easy to wash. One has, however, noted that due to the forming methods considerable internal stresses are obtained in the latticework. These may cause a non-desired deformation of the bottom of the crate and its walls which cannot be tolerated.

It is therefore an object of the invention to eliminate or at least considerably reduce these stresses. This problem is according to the invention, solved by insertion of stress relieving rings in at least certain of the intersections of the lattice network.

A more particular object is to provide an improved crate structure in which the bottom of the crate is moulded from plastic material and constituted by a crisscross network of diagonally extending bars which intersect one another at their mutual crossing points. Stress relieving rings are incorporated into some of the intersections between the bars to prevent deformation of the bottom in the event that initial stresses are developed in the bottom as a result of the moulding operation. The rings are arranged in mutually perpendicular rows along the bottom and are located at every other intersection along each of the diagonally extending bars.

The invention will now be more closely described with reference to the accompanying drawings, in which:

States Paten ice FIG. 1 is a perspective view of a crate upon which the invention has been applied.

FIG. 2 is a bottom view of the crate, and

FIG. 3 is a cross-sectional view of the crate along the line III-III in FIG. 2.

The crate as shown in FIG. 1 generally consists of two short side walls 1; two long side walls 2; and a bottom 3.

FIG. 2 more closely shows the design of the bottom 3. From the figure, in which the bottom is seen from below, it is apparent that the bottom has the shape of a lattice, i.e. a criss-cross network consisting of diagonally running bars. The bars run from below left up to the right, as the bars 4 and 4", and from below right up to the left, as the bars 5' and 5". Conventional intersecting structure between the two sets of diagonally extending bars, as for example the points where the bars 4 and 5' or 4" and 5" cross, are broadly denoted by numeral 6. In other intersections, however, rings 7 are structurally incorporated for the purpose of relieving stresses in the lattice. Numeral 7a stands for a ring which join the bars 4" and 5', and 7b is a ring which connects the bars 4 and 5" with each other. The rings 7 are arranged in mutually perpendicular rows and are located at every other intersection along each of the diagonally extending bars.

Some of the rings are completely filled with plastic. These completely filled rings, as the ring 8, define the injection points for the plastic material.

In the case of stresses in the crate bottom, e.g. thermal stresses, the rings 7 function as stress-absorbers in that they can be compressed as well as expanded. If the stresses are symmetrical the rings 7 in both the cases will tend to assume a square shape.

We claim:

1. A crate structure including a bottom moulded from plastic material, said bottom being constituted by a crisscross network of diagonally extending bars which intersect one another at their mutual crossing points, and stressrelieving rings incorporated into some of the said intersections between said bars to prevent deformation of the bottom in the event that initial stresses are developed therein as a result of the moulding operation.

2. A crate structure as defined in claim 1 wherein said stress-relieving rings are located at every other intersection along the diagonally extending bars.

3. A crate structure as defined in claim 1 wherein said stress-relieving rings are arranged in mutually perpendicular rows and are located at every other intersection along the ldiagonally extending bars.

References Cited UNITED STATES PATENTS 2,850,153 9/1958 Cosentino 22083 3,107,026 10/1963 DeChelbor 22.0-21 3,223,280 12/1965 Kazimier 220'-10'2 FOREIGN PATENTS 659,127 3/ 1963 Canada.

JOSEPH R. LECLAIR, Primary Examiner.

I. R. GARRETT, Assistant Examiner.

U.S. Cl. X.R. 52669; 220-83 

